Oracle 11g high IO Wait

Question 1

The problem solved..... The cursor_sharing is made to force... This reduced the IO very much. Now IO is normal in all instance. Then we created two indexes for the same query which recommended by sqltuning advisor and accepted the profile

2- SQL Profile Finding (see explain plans section below) -------------------------------------------------------- A potentially better execution plan was found for this statement.

Recommendation (estimated benefit: 80.44%)
Consider accepting the recommended SQL profile. execute dbms_sqltune.accept_sql_profile(task_name => 'my_sqltune_task1', task_owner => 'IMUSE01', replace => TRUE);

Validation results ------------------ The SQL profile was tested by executing both its plan and the original plan and measuring their respective execution statistics. A plan may have been only partially executed if the other could be run to completion in less time.
                   Original Plan  With SQL Profile  % Improved
                   -------------  ----------------  ----------   Completion Status:             PARTIAL          COMPLETE   Elapsed
Time(ms): 31479 8049 74.43% CPU Time(ms): 5172 1656 67.98%
User I/O Time(ms): 16367 3422 79.09%
Buffer Gets: 265365 51818 80.47%
Disk Reads: 3227 524 83.76%
Direct Writes: 0 0 Rows Processed: 0 20000 Fetches:
0 20000 Executions: 0
1
3- Index Finding (see explain plans section below) -------------------------------------------------- The execution plan of this statement can be improved by creating one or more
indices.

Recommendation (estimated benefit: 81.1%)

Consider running the Access Advisor to improve the physical schema design or creating the recommended index. create index IMUSE01.IDX$$_67E5B0001 on IMUSE01.SUBSCRIBEINFO("STATE","SUBFLAG","MONTHBILLID","RETRYENDDATETIME");

Consider running the Access Advisor to improve the physical schema design or creating the recommended index. create index IMUSE01.IDX$$_67E5B0002 on IMUSE01.SUBSCRIBEINFO("STATE","MONTHBILLID","FAILTIMESTAMP");

Rationale --------- Creating the recommended indices significantly improves the execution plan of this statement. However, it might be preferable to run "Access Advisor" using a representative SQL workload as opposed to a single statement. This will allow to get comprehensive index recommendations which takes into account index maintenance overhead and additional space consumption.

4- Restructure SQL finding (see plan 1 in explain plans section) ---------------------------------------------------------------- Predicate "O"."NEXTCHARGETIME"<>:B1 used at line ID 5 of the execution plan is an inequality condition on indexed column "NEXTCHARGETIME". This inequality condition prevents the optimizer from efficiently using indices on table "IMUSE01"."SUBSCRIBEINFO".

Recommendation -------------- - Rewrite the predicate into an equivalent form to take advantage of indices.

Rationale --------- The optimizer is unable to use an index if the predicate is an inequality condition or if there is an expression or an implicit data type conversion on the indexed column.

Question 2

The problem is that the statement is causing more than 50000 disk reads. This is probably caused by using cursor_sharing. This parameter is generally used if the application is coded without using bind variables (very bad. Don't walk, run to fix that application). Probably you even set cursor_sharing to force, which can have undesirable effects like the one described and cursor peeking will also not work in most cases.

You might work around it by specifying hints to avoid the full table scans depending if you have indexes on the required tables. As you do not describe that, it is not possible to give you any concrete advice.